DIY Fuel Pressure Modification - Honda CRF1000L Africa Twin Forum
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post #1 of 6 (permalink) Old 03-12-2018, 06:58 PM Thread Starter
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DIY Fuel Pressure Modification

I am in the final stages of testing a solution to the stalling/ rough running issue (and other running problems)

I have a 2017 tri color that i have installed a modified fuel pressure regulator.

Some back ground, I owned
TurboCity (retired 2 years ago) and have designed and built modified FPRs for ST1300, VFR800, Goldwings, CBR1000. (search Turbo City FPR)

I have also done extensive GM automotive computer modifications and programming.

All of these Honda EFI computer systems run lean and that is what causes most all of these issues. By raising the fuel pressure slightly, most issues disappear without creating problems with the computer.

I have identified a readily available replacement FPR regulator that when modified works great in the AT, and its less than $25.00. Easily installed by just removing the fuel tank (no other plastics need remove). No modifications to the original fuel system (easily returned to stock)

Can be used to improve fueling with aftermarket air filters and exhaust.

When testing is complete, I will provide part numbers of the regulator and complete instructions on how to modify (very easy).


Fuel Pressure Regulator (FPR) modification.
CRF1000 AT fuel pressure spec 47-53 psi measured 50 psi

Aftermarket FPRs that should work I used the autozone 800-484
--------------------------------------------Standard
-----------------------------------------------motor
---------------------------------------------products ------Autozone
Honda accord regulator (03-07) ---------pr335------- 800-447------ 50psi approx $25.00
Honda S2000 regulator (06-09)---------- pr368 ------800-480 ------ 51psi approx $25.00
Honda Civic regulator (03-05) ----------- pr372 -----800-484 ------- 48psi approx $25.00

tools required:
fuel pressure gauge
air compressor
small arbor press or drill press
hose and clamps

Process:
remove the o-ring and slip hose on the inlet to the FPR, secure with clamp.
position the FPR in the arbor or drill press with the hose pointed down/ cap up.








use a "T" to connect the fuel pressure gauge to the air compressor and the hose to the inlet of the FPR.
increase the air pressure until the fuel pressure gauge stops increasing (should be 48-50 psi) which is the stock pressure of the unmodified FPR.
continue to increase the air pressure until the air source pressure is around 60-70 psi- the fuel pressure gauge reading should not change at this time.




position a small spacer on top of the FPR (the outer diameter of the spacer should be just smaller than the recessed area on the cap of the FPR) 8mm 1/4" drive sock works great.
bring press down to top of FPR.

slowly increase the pressure of the press, watching the fuel pressure gauge.
adjust the press so the FPR reads 54-56 psi. go slowly and carefully. the new pressure CAN NOT be lowered if you go too far.
54-55psi works well on stock systems, 55-56psi should work well on systems with aftermarket exhaust systems.









release the press - verify the new FPR pressure is where you want it. The pressure will lower slightly as the press is released. you may need to repeat the process if the pressure lowers too much.

to use this regulator a 170mm x 4mm O-ring will be required as a spacer when installing into the CFR1000 fuel pump assembly.














Installing the regulator: use the factory service manual for details.
This is best done with the tank near empty of fuel

Remove the front seat.

remove the lower fuel tank trim on both sides.
remove trim piece at rear of fuel tank

remove seat catch stay (2) bolts and seat catch hook (1) bolt

remove ETC tray- release fuse box(s) -main wire harness clip- dummy red connector- main harness clamps
remove the 4 push pins on tray at rear of fuel tank.

remove bolt at rear of fuel tank.

separate the side fairing mid panel tabs from the grommets on the side of fuel take- the panels do not need to be removed.

lift at rear of fuel tank and slide toward the rear a couple of inches. (easier with a helper- the side panel tabs will try to drag on the tank)

when clear of the side panels, lift the front of the tank to access the wires and hoses under the tank.

the fuel line is released by pushing in and down on the tab. once released, the line will easily separate- do not force apart. some fuel will spill from the hose.

disconnect the vent hoses from the tank.
disconnect the wiring plugs (2) at the rear

remove the fuel tank.

turn the tank over and remove the fuel pump assembly (6 nuts)- note 1 is a cap nut.

on the side of the fuel pump assembly, there are 2 screws with wires- remove the screws.

locate the tabs (4) around the center of the fuel pump housing assembly. release the tabs and remove the filter assembly ( may need to gently pry to separate).

remove the original FPR from housing- it just pulls out.

install the new FPR in the housing with the 170x4 o-ring between the FPR flange and the upper (mount) part of the fuel pump assembly.--- the body of the new regulator is slightly shorter than the original- if the o-ring is not used, the lower sealing o-ring fits too far down in the house and the system will not generate any fuel pressure (indicated by the fuel gauge flashing when you try to start the engine)

reassemble everything in reverse order.



I have put over 2500 miles on the modified FPR to insure that there are no issues.

I find; NO stalling on start up
stronger, smoother idle.
greatly reduced deceleration popping
reduced engine vibration 3-5k range
less throttle required to hold a cruising speed.

I do not want to claim that there is a performance/ power increase- that will be for you to decide.

the only negative i see is a very slightly reduced fuel economy in around town, low speed riding- the cruising fuel economy improved very slightly when on the highway.

If any one is local in So Cal, if you purchase the regulator, I will help you modify and install at no charge

PM me if interested

Thanks Tom
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Last edited by turbocitytom; 03-12-2018 at 07:02 PM.
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post #2 of 6 (permalink) Old 03-12-2018, 07:20 PM
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Looks to me like you are going to a lot of trouble to treat a symptom instead of searching for a root cause. I have 10k hard miles on my 2017 with never having suffered rough running or engine stalling which indicates to me that your AT is likely suffering from a component failure, not an engineering failure.
Instead of jacking up the fuel pressure that will likely just mask the root cause of the real problem, I think I will just troubleshoot the factory system if my scooter ever exhibits such symptoms. Looks like you are having fun, though...
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post #3 of 6 (permalink) Old 03-12-2018, 08:01 PM Thread Starter
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Quote:
Originally Posted by fuelpincher View Post
Looks to me like you are going to a lot of trouble to treat a symptom instead of searching for a root cause. I have 10k hard miles on my 2017 with never having suffered rough running or engine stalling which indicates to me that your AT is likely suffering from a component failure, not an engineering failure.
Instead of jacking up the fuel pressure that will likely just mask the root cause of the real problem, I think I will just troubleshoot the factory system if my scooter ever exhibits such symptoms. Looks like you are having fun, though...
I used to think my AT ran great- debated for a long time as to if it needed "fixed"- after raising the fuel pressure, it runs fantastic. I'm glad you like the way yours runs, but that doesn't mean that it can't run better.

Thanks Tom
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post #4 of 6 (permalink) Old 01-24-2019, 03:28 PM Thread Starter
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Hi Everyone, I now have over 26K miles on my 17 AT. After testing pressures from 53-58 psi- 54-55 is the sweet spot. I have done several more of these on others AT's and have had great results. It is a shame that i read all of these posts about poor running, stalling, hesitations- this is the easiest fix- our EFI systems are just too lean. A little more fuel pressure works wonders. Easier install/ cheaper than anything else available. A computer reprogram is the best fix- but costly. all these other devices that "fool" the computer will produce like results- they are just different ways to trick the system into running richer.


The new ATAS uses the same fuel pressure regulator and should respond the same even though the system is slightly different (drive by wire)



Thanks Tom
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post #5 of 6 (permalink) Old 01-24-2019, 04:24 PM
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Tom: I for one thank you for what you have so generously given to the group, and I have copied it and it will be going into my shop manual for the future. I just wish that i were in So Cal (only temporary you understand :-) ) to take advantage of your assistance. Van
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post #6 of 6 (permalink) Old 04-20-2019, 09:24 AM
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Hi Tom, just read your posts which I also thank you for, I have a 2018 Atas which I havenít noticed an issue with yet! But have just had to leave it a Honda dealer running sick as a pig, cutting out missing & coughing & farting, stop & switch off a couple of seconds and then runs better go a few minutes so I assume I have a map sensor or pump/ pressure issues. But in warranty so hopefully it should come back fixed!! Is this worth me looking at possibly altering f/p as not noticed too much of an issue but it only has 1200 miles on at moment, so now weíre getting into spring i will be clocking up a lot of miles over the next few months, you obviously have the technical knowledge for what youíre doing unlike most people on these forumís!
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